New communications devices with advanced data capabilities have been brought to the market that allow the devices to connect to the broadband services, such as Internet, wirelessly. These new devices create an increasing demand for higher data rate and bandwidth to wireless service providers and operators. In order to meet these demands, dual carrier high speed downlink packet access (DC-HSDPA) was introduced in Release 8 of third generation partnership project (3GPP) to increase the throughput and provide efficient load balancing across carriers. Dual carrier high speed uplink packet access (DC-HSUPA) was also introduced in Release 9 of 3GPP to increase the uplink (UL) average and cell edge user throughputs. Both DC-HSDPA and DC-HSUPA offer a capacity gain from system performance perspective through aggregating multiple carriers on the downlink (DL) and the UL, respectively.
Continuous Packet Connectivity (CPC) was introduced for increasing the number of packet data users, (i.e., high speed packet access (HSPA) users), in the universal mobile telecommunication systems (UMTS), where the users stay connected over a long period of time with occasional active periods of data transmission, and avoiding frequent connection termination and re-establishment. Completely releasing dedicated channels during periods of traffic inactivity would cause considerable delays for reestablishing the data transmission. However, maintaining the control channels will significantly limit the number of users that can be efficiently supported due to a noise rise on the UL. CPC is intended to reduce the impact of control channels on UL noise rise while maintaining the connections and allowing a much faster reactivation for temporarily inactive users.
As the key features of CPC, discontinuous reception/discontinuous transmission (DRX/DTX) in a Cell_DCH state was introduced in Release 7 to save UL capacity and extend user equipment (UE) battery life during inactivity periods while providing users an “always-on” experience. In Release 8 and Release 9, a single DRX state machine is maintained across the DL carriers for simplicity, and two independent DTX state machines are maintained in the UL for a better UE DTX gain.
With the rapid increase of data usage, HSPA is expected to be deployed on more than two carriers. Multi-carrier operations allow a UE and a network to receive and transmit on two or more carriers, thus increase the capacity of the system. Release 10 of the 3GPP supports up to four HSDPA carriers spread over one or two frequency bands and up to two adjacent HSUPA carriers. Recently, eight carrier HSDPA (8C-HSDPA) is proposed for Release 11 of 3GPP to further exploit the available spectrum to achieve substantial gains in terms of both cell and user throughput.